This invention relates to an electro-synthetic method for producing alcohols and carboxylic acids from their corresponding metal salts while also recovering valuable metal cation residues free of the alcohols and carboxylic acids. In so doing, this invention provides desirable synthetic routes to alcohols and carboxylics, as well as highly effective treatments of mediums containing the metal salts, including for instance byproduct streams, to recover valuable products therefrom.
As further background, alcohols, carboxylic acids, and metal cation salts all enjoy wide varieties of uses. Alcohols, for instance, are widely used for organic synthesis, as solvents, detergents, beverages, pharmaceuticals, plasticizers, and fuels, while carboxylic acids find utility in organic synthesis as well as many other applications. Further, metal cation salts include some of the most widely used chemicals in the world. For instance, metal hydroxides, e.g. sodium hydroxide and magnesium hydroxide, are used in very large quantities in chemical manufacture, refining, and in the production of pulp and paper, detergents, textile processing, etc.
The alkalai metal salt counterparts of carboxylic acids and alcohols are also useful in organic syntheses and other applications. However, there are many situations in which it would be most desirable to convert these alkalai metal salts to their corresponding alcohols or carboxylic acids. Further, because metal cation salts such as caustic materials (e.g. alkali metal hydroxides) are considered valuable and relatively expensive especially by those familiar with their high-volume use in many commercial scale reactions and other settings, it would also be highly desirable to be able to recover the metal cation residues liberated during such conversions, for instance as hydroxide salts.
As an example, large quantities of alkalai metal (e.g. sodium) salts of carboxylic acids are present in the byproduct stream from production of trimethylolpropane (TMP), a large-volume intermediate primarily used as a glyceride substitute in alkyd resins, in flexible urethane foams, and in synthetic lubricant base stocks. See, Chemical Economics Handbook, SRI International, pages 682.7001 U and W, 682.7002 V, and 682.7003 I (August 1985). TMP is currently made by reaction of three equivalents of formaldehyde with n-butyraldehyde. The initial step is a condensation reaction catalyzed by base (e.g. NaOH) and thus little if any NaOH is used in this step. However, the final step of the reaction is not catalytic: it is a Cannizzaro reaction in which an entire equivalent of caustic base is consumed, producing TMP and sodium formate. The byproduct stream from this TMP synthesis has an equivalent of sodium formate. In this instance, significant commercial and technical advantage could be gained from conversion of the sodium formate to formic acid, while also recovering the valuable sodium hydroxide for use in another TMP synthesis or otherwise. An additional benefit would be gained if the treatment of the byproduct stream also allowed for survival and facilitated recovery of any remaining TMP in the byproduct stream.
As another example, phenol is a valuable alcohol having many and diverse uses. Currently, most phenol worldwide is made by oxidation of cumene, with acetone occurring as a byproduct. The initial reaction step yields cumene hydroperoxide, which decomposes with dilute sulfuric acid to form the phenol and acetone as primary products. As a result, the commercial supply of acetone is largely tied to its occurrence as a byproduct in the production of phenol.
Minor amounts of phenol are produced by still other routes. For example, some is produced by the Dow process in which chlorobenzene is reacted with sodium hydroxide at elevated temperatures to form sodium phenoxide and sodium chloride. The phenoxide is then treated with hydrochloric acid to yield phenol. Another less-used route to phenol involves the fusion of benzenesulfonate with alkali at elevated temperatures to form sodium phenoxide, which is then treated with dilute H.sub.2 SO.sub.4 to yield the phenol. These processes are undesirable because two equivalents of valuable sodium hydroxide are consumed.
It is evident from the foregoing that the need exists for improved synthetic routes to alcohols and carboxylics. Equally evident is the need for an improved way to treat mediums containing corresponding metal salts of alcohols or carboxylic acids, including for instance byproduct streams containing metal salts of carboxylic acids, to recover valuable products therefrom in a form that requires little or no further processing prior to use. The applicant's invention addresses these needs.